Tanssiaiset

#include <iostream>
#include <utility>
#include <vector>

using namespace std;

int main()
{
	int n, m;
	cin >> n;

	m = n / 2 + 1;

	vector<int> vl, vr, c;
	vl.resize(m);
	vr.resize(m);
	c.resize(n + 1, 0);

	vector<int> s;

	for(int i = 0; i < m; i++)
	{
		cin >> vl[i] >> vr[i];
		c[vl[i]]++;
		c[vr[i]]++;

		if(c[vl[i]] == 2)
			s.push_back(vl[i]);
		if(c[vr[i]] == 2)
			s.push_back(vr[i]);
	}


	for(int i = 0; i < m; i++)
	{
		if((vl[i] == s[0] || vl[i] == s[1]) && (vr[i] == s[0] || vr[i] == s[1]))
		{
			cout << vl[i] << " " << vr[i] << endl;
			return 0;
		}
	}
}

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: ACCEPTED

Test 5

Group: 1

Verdict: ACCEPTED

Test 6

Group: 2

Verdict: ACCEPTED

Test 7

Group: 2

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED